Fix app opt compile failure due to missing <inttypes.h>

opt.c uses functions that are only available if inttypes.h exists.
It now checks a define which is unavailable if
inttypes.h is included. The include is done automagically inside e_os2.h.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8986)